pathology

Chapter 61 Endocrine pathology




Questions


image Which diseases can result from hyperplasia or atrophy of endocrine glands?

image What are the most common tumours that arise within the thyroid gland?

image What is Cushing’s syndrome?

Much of the pathology of endocrine organs is related to hormone excess or deficiency. Typically, excess hormone production is associated with hyperplasia or neoplasia of the endocrine cells producing the hormone. Deficiency of a hormone is usually associated with atrophy of the endocrine cells or their destruction, depending on the pathogenesis.


Neoplasms of endocrine cells are common. They can secrete excess hormones, in which case they can manifest clinically through the hormone effects (Fig. 3.61.1A). Neoplasms that cause clinical effects by secreting excess hormones are called functioning tumours, while those that do not produce clinically apparent hormones are called non-functioning tumours. If a non-functioning tumour destroys the gland in which it has arisen, there may be a lack of hormone production and clinical presentation is with hormone deficiency (Fig. 3.61.1B). Endocrine neoplasms can also have non-endocrine effects (Fig. 3.61.1C).


image

Fig. 3.61.1 Possible effects of neoplasms of endocrine glands.




Hyperplasia and atrophy of glandular tissue


Glands can be hyperplastic either because they are autonomously hyperactive or because they are being excessively stimulated by a stimulating factor. An example of the former is primary hyperparathyroidism. In this condition, primary hyperplasia of the parathyroid glands is associated with an autonomous increase in parathyroid hormone secretion. An example of excess stimulation by a factor produced outside the gland is Graves’ disease, in which the thyroid-stimulating hormone (TSH) receptors on thyroid epithelial cells are abnormally stimulated by an autoantibody, causing enlargement of the thyroid gland and excess hormone production; the excess of thyroid hormone produces a constellation of clinical features called hyperthyroidism.


Although hyperplasia of glands is often associated with excess hormone production, it can occur without an excess of hormone production in some circumstances. For example, in iodine deficiency, the thyroid gland enlarges even though there is a deficiency in thyroid hormones (hypothyroidism). Iodine is required for the synthesis of thyroid hormones, so there is a failure of production of thyroid hormones in iodine-deficient individuals. One result of the reduced circulating levels of thyroid hormones is increased TSH production, because of decreased negative feedback on the pituitary gland. The increased TSH causes thyroid hyperplasia.


Atrophy of glandular tissue is usually a result of lack of a stimulating factor. For example, hypothyroidism caused by lack of TSH is associated with atrophy of the thyroid epithelium.

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Jul 3, 2016 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on pathology

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